Automatic telephone system.



A w. E. LAMB.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED IUNE 26.1912 EENEWED DEC. I9. 1911- W. E. LAMB.

AUTOMATIC TELEPHONE SYSTEM.' APPLlcmoN mw mm2 26. 1912. RENEWED Dic. I9. 1'9|1 s sHEE's--SHEET 2.

Patented Ang. (5, 1918.

w, LAMB. AuToMATlTELPIjQNE SYSTEM; APPLICATION FILED JUNE 26\ 19 l2j`RENWED DEC. I9. |917.

1,275,186. Paten/ted Aug. 6, 191s.

l' N s f N llllllHlIl W A MEWQR-f UNITED STATES PATENT OFFICE.

WILLIS E. LAMB, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A. CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application ined :une 2s, 1912. serial No. 705.908.

To nl! wlw/n it may rom-ern.'

lle it known that l. )Vinms ll. LAME, a citizen of the United States ot' America. and resident ot' Los Angeles. in the county otf Los Anfelrs and State ot' California. have invented certain new and useful Improvements in Automatic Telephone Systems. of which tinI following is a specification.

My invention relates to automatic telcphone systems. and particularly to systems which emploi' primaryfand secondary line switches.

In auch systems these primary and sccondary line switches are divided into groupsl or boards. and truuk linesl leadingl out from cach group ol primary line switches arev dist'ril'mted equally among a plurality of groups of secondary line switches. There areI usual-ly ten groups of secondary line switches, Aso that one trunk line leads from each primary group to each secondary group. The. number of secondary line switches in each'grouln and therefore the number of trunk lines leading .into each group. is generally greater than the number of trunk lines leading out from the -lroup. Tt will. therefore. be seen that if all the trunk lines `leading out of any particular secondary group are iu use. there will still be some idle trunk lines leading into that board` and it. therefore becomes necessary to provide some,V means for preventing the primary line switches from selecting these idle trunk lines. Hcretofore this has been accom plishcd by causing a guarding potential to he placed upon the primary master switch contacts 'of all the trunk lines leading into a lsecondary group when all 'the trunk lines leading out of that secondary group are .in use. This guarding` potential prevents any primary line 4switch from obtaining ronnection with a trunk line-leading into a busy secondary board. provided alloiLA the idle primary line switches are in locking engagement' with the plunger' shafts so as to be under the control of the'master switches. In certain types of line switches, however, thesev switches are so arranged that,aftcr one has been operated to select a trunk and then released. its plunger or Contact arm remains standing in front of the trunk line with which it was last engaged until the plunger shaft1 by subsequent operations` ret-urns to theI positionv in which it was when the line switch was operated. 'In such switches it Specification of Letters Patent.

Patented Aug. 6, 1918.

Renewed December 19. 1917. Serial No. 207,979.

will bc seen that there may be as many as mue out of a group of ten line switches on each primary board which are not under theI control of their master switch, and any one of these may be standingr opposite a trunk leading into a busy secondary board, and the simple operation of puttingr a guarding potential upon the master switch bank Contact will not move this line switch. away from the trunk leading into the busy secondary board.

An object of my invention -is the' provi sion of means to absolutely insure that no primary line switches shall make. connection with a trunk line leading into a busy secondary board. In order to accomplish this it is necessary to provide, in addition to placing a guarding potential upon the' prirnary master switch bank contact-s of the trunks leading into a, busy secondary board, means whereby the primary master switches are caused to pick up. yall the idle plungersI belonging` to the respective lino switches and bring them into locking enit' gagement with their plunger shafts. This is accomplished by causing all the primary master switches to go through a complete operation each time all of the trunk lines leadingout of a secondary board are in use.

A further and special object of my inrention is the provision of means' whereby all of the primar master switches which have trunk lines leadinginto a secondary board are not operated simultaneously. Such simultaneous operation `would be objectionable. as it would cause a large momentary consumption ot' current. I thereforo providespecial means in which a small number of primary master switches are brought successively into operation, whereiby the maximum current consumed in operating all of these master switches is greatly reduced.

These and other objects of my invention i 100 the. samer'tyi'e asithat'lfshovrn and described'- in .-Britie-"l No. 1421-o ing and calledfffsubscribers established throughthe medium of primary andvsecond `and C, selectors Rieccomi' selctors F the. switch which operates in response tothe -opera-tionfof the 'substation -ca y 'for y the. first -digit of th'e called number. Thelrst selectorE is not, permanently I ncctd'with the callingline, but-the calli l subscriberobtains connectiontherewit thlrinigh the medim of twjo';prelimilia'l'y'4 trunking switches C and Q."whi'chnre oper- ,ated immediately upon' the removal of his receiver.' The Switch C'is individl11`\l to the su'bscribers line. -Theindivdualswitches C 'of all the lines-'in the system-aejar`ranged in grmipS, usuallyA one hundred in a group, each grou having-common access to' av small 'numlger of trunk lines which' lead toY 'second ary Y switches C?. Thes'e secondary primary switches,` each group hayingfaccess' topa-'pluralityof trunk linesleading to l Selectors The trunk- -1 ir 1 es which' lead.

'v `from Y any:4 particular .group ofrfprimary 'switches'C d onot lead -to secondarylswitehes whic h.are all included-m the same-group,

10eme .in s pluralityjof groups' of Second-- first Selectors considerably larg'eith'a'n the' ofiprimaryf line'switches are-made accessible 11i common toa .plurality gronp'j t' ofsubscribersf; j The automatic 'subsv tionshown herein may be of any suitable or approved type ofautomatic substation. Reierringto subfl l Station'AQtheslbSffations 'shown herein prise the usual receivjer 2, transmit-ter. 3,#

' 'yrovided-with an. automatic calling device.

' Went .to Aleix-ander E. Kei'th i dillo-that" is, it is' lltsystem in which the connections" between-'-the"call`,

' ter switch D Ain this case is'somewhat difary preliminary trunk-selecting svritehes vC and connector'sH; The first selector E is controlled Vby the armatureof the relayl switches areV arranged in f groups, .like 'the biit'are distributed among Secondary Switches a'l'y switches. "11n thls manner'ja number ofpositions by the engagement vo f the spring 1 9 with the-'detent onthe under` s ide'of the his .calliiigldevice'inayf b e 'of the Atype shown and;v described British patent to" S.- G. SL

Dicer, -No. 23,654 of 1916,v '1 As shown here 'ed diagnammatically by apair 'of impulsesprings 7 and Slandjatootlieiiimpulse wheel emana; seeming. h SFI-are 'essentially theY same 'asf inlBritish Patent No. -1421 'of osite the bank terminal of an idle trunkv ine by aso-'called 'master switch. The masferent from' that shown in-said British Patent No@ '-1421 f- 1910'. As shown in -I4`ig.4, 4 I mensual. plunger shaft 1'0, through the medium of which the master 'switch controls 17 5 thef'plungers, -is connected with a 'rota shaft l'insuch a manner thatas-the-shat 10 is rotated back and forth, the plunger' shaft is caused to, osc'illateaboutsaid shaft 10 as an axis. The shaft 10fis adapted -to beA rotated4 vinj one direction by a spring 11 and in the other direction against the opposition of said/spring .by a' solenoid 12.- Securecl vto the shaft'lO' there isa cam inember 13 provi'ded along its outer-edge with -a series of notches 14, onefo'r each trunk line to which theline switches have access. The shaftlv is normally locked' againstrotation in either direction by the engagement-of the lever 15 with one ofthe notches 14". The l'everfli's ergi'zedthe'leveriswithdrawn from the ,cam l so as to unlock the 'shaftlOf Thes' eed of l slpeedfof the plungershaft, is controlled t rotation of the shaft '1 0 and there ore the.;

logh. the mediunioia suitable'governor 17., Associated with the master switoli" -beng operated, vare-'locked 'in their oper'atedf spring 20. The Springs are unlocked' by 4the arm 21 when thefsha ft IQ'rea'c'hes the-'liniit'ofA its travel inlone'f lirection.vv When lthe shaft w 110- reaches -the limit. of its travel in the' intojengagelhent g with the spring@ 2 'I segment 25 and 'an indiyiduallcontact. 'a' for tion withr the individual contacta .cor' 1 l responding tothe trunk line"v before which A I .the'plung'ers ofthe Aidle` -lineswitches' are re'stingf l"In 4gerieal,"thel operationv ofp'theff in, -howeven the calllng devicel 1s `represent-v trunk 'line vis'seized by a line' sWitch, -the rel' the spring 1I thereupon vrotati'n'gtheshaft 10 to 'cause the plungershaft vto 'inoyethe Y idle'dplungersfawa frmftheptrunk just Seize enfthe 'and' to an id e vtrunk" line.l

idle l trunk Vline is reacheiL'the relay- I6v deen ergizes 'and againv locks tl-iej shaft. i When.'

.105,A -other direction, the arm'22'ifor'ces the's'prin come locked in their operated positions. Thieloses the eireuil of the solenoid 1:2.

, which rotates the shaft 1() bark in the, 0p-

that shown in Fig. 4. with the addition ot a number of circuit-controlling relays. the. functionuof which will be explained hereinafter.

The device shown at L is couiiiion to all the groups of primary and seeondary Switches which are assoeiated together. This device comprises a rotary wiper 2T which is adapted to rotate in a stepdiy-step manner over a bank of eontaets Il. There, are as man)I eonlaets iu the haiik b as there are groups of primary line switelies (l. There nia'i' be a plurality ot eontarts to be engaged bythe wiper 2T in eaeli stepl i`\wstep position. neeted to the starting relay tifl ot' a different master switeli I). The wiper is rotated Vthrough the niediun'i of'a motor magnet 29.

The magnet 3() is a holding magnet which. when energized. prevents the wiper from rotating baekiiard. The `springs 31 are adapted to be separated by the wiper :27 when it is rotated beyond the last set of contacts.

The seleetors ll and l" and the eoniieetor ll are of the general t \'pe of seleetor and eoniieetor. switelies diselosed in Vnited States Letters Patents Nos.V 815.5521 and 815.170. respeetii'ely.4 granted Marel: 13.y 19116. to Keith` llriekson and Eriekson. The

circuits are modified. however. as shown in said British Patent 'No 1421 hereinabove referred to.

i Tlieline switeli C are in all respeets the A and line switch C.

and the substation` A2 saine as the substation well known. the plunger ofthe line switch C of the calling line, is normally held opposite theterininal of an idle trunk line. When Eat-h eontaet in the bank is con# At. M (Fig. 3) tliere'is shown a ringing .eurrent generator and at S a bus)v signaling the ealling subseriber renimes his reeeii'er preparatory to making a eall. the elosure of the hook switeli springs Il! and Z155 eonipletes a bridge aeross the ralling line through the transmitter and reeeirer` whereupon the line. wiiuling 254 ot' the switrh (l heroines eiiei'- gized. 'l`lie winding 2*4. upon energizing. at-triiets the armature lli. wliereb the rircuit oil the operating winding It is elosed. 'l`lie winding 151'. upon energizing` attrarts the, plunger ariu 13T and the eutotl armature Z55. 'llie armature llt# operates to diseonneet the. line windingJH l'roni the line. while the pli'uiger arni 21T causes the plunger to be thrustY into the group ol' eoulaet springsl forming the tei'iniual olI the triliik line before, whielrit is heilig held aiul t'ories the springs ltl. 4U., l1` 42. 425. 44. 43 and l-i into eontact in pain. as'sliown. 'l`he engagement ot' the springs lt and -ll with the springs 4tl` and 42. respeetivel); extends the line eireuit through to they springs 4T and 4h ot' the switch ("1 'l`he engagement of the springs 45 and lf3 ol the swileli eonipletes :i eireuit extending from ground (l through thi springs l and 411. winding lll ot' the 'switeh C, springs 50.51. 52. 521. 54. :35. TS1 aiul TS l to the battery lead Titi. thenee through battery l5 to ground (i. 'l'he winding 421. upon energizing, attraets its plunger arin 5T. which operates in thel saine inaiiiiei' as the plunger arni oll the switeli to extend the line eoiinectioiiover the trunk ronduetors 5H and 59 to a l'irst' seleetor l'l (Fig. 2), \\'lien the )vinding ol' the switeh (VZ is energized it, also attracts the aruiatui'e ($1. whieli oiierates t0 insertV the high resistanee winding (i2 in series with the winding 49 to reduee the eurrent. consumption while. the switch is being held in 'its operated position. Then eoniieetion is extended to the lirsl seleetor ll its line relay ($25 lieeonies energized and rloses the circuit of the rela t'il.- 'l`lie rela \l (34. upon energizing` eonililetes a rireuit extending t'roin ground (l2 through the springs (l5.

the holding winding (iti ot' the switeli (`to` is assumed to lie'standing on the eontaet.

.)H at the time)` eoninion segment 25 and the rela)Y (lil to th'e hatter lead t'. 'l`lie. relay (tt), upon energizing, eoniplet'es an energizing eireuitl for the relay lt'. relay 1V thereupon operaties to open the springs 7l and tolclose the springs 72. rlhe izo .60' v .theplimerishaftqto.the position .in .which opening of the springs 71disconnects the op-` erating windingsofvall theswitches C fromA fthe battery lead."56. The. closure of the s rings 72 is without any' particular func-- tion at this time- I The rela 16, upon ener-v gizin'g, also operates to-wit draw the-lock- 'lngrarml `from the cam 134 (F1g. 4), therej -by .releasing thejshirft 10 and permittlng 1t to' be' rotated by 4the spring 11 tocause'the ing1 opposite the next trunk-line. Ifthe next trunk lineafterfthe one seized by the 'switch G hasbeen busy, the wiper 26 would have foundthe next. contact grounded and Y the.. relay 16 would have. remained ener- VAgzeld"and caused the Ehmg'er to lbe rotated "2'i-pastja'll the busy trun s to 'anidle fone.

When -the bank springs 73 and '74 are switch 02,'the master switch D caused to 'advanceth plungers of4 allthe'ldle secondi y switches C2 'which' it controls to an D corresponds ,to the relay 69 of the 'switch D.. n.

" ,1s-thus evident that when all the .trunk lines leadin out of- 1a secondary group becorne ;`f bi1sy',tt lere will vstillbetrii nk lines leading .into said. group which 'are' idle and means slould 'bje provided' to keep any ofthe pri# maryf'switches' from seizing one of these '.-idlei 'incon'ijn trunks? While 'the .outgolng' j ltrunks" ere-dl. busy-,"Thig .0f-course, can

*be done-by. preventing the master switches@ .of the" riirnary groups-from 'stopping theirp vlingers restinv in front vo'a `trunk v l corne. .locke d. v. rith .t

'i Said switches do ntcome under the v"control When. the plungers have been extendin spri gs necte' in series, so thatwhenall theserelays ,as to prevent thernaster switch D from opprimary master switches -D to .prevent theprimary switches from stopping oppositg; a' trunk line leading. to aj secondary, 'switch on'i ff at board whose'outgoing-trunk lines' ere all.-

8 0Sby the' re1ay,77 complete'sAa/clrcnitf of-.llicl meister" s'wi-tch again until .the master' switchg by subsequent'operatio'nsgV .returns Lamme. 1

i, mainfin position to seizesJ trunk line lead-.

ing into a secondary grou whenA "all the trunkvlines leading out 'o -it arein use, it is; lI iecessary to cause, a1l@the prlmalyf, master switches toA be operated so as tolceu'aehmy allthe'idle plungers of the Iprimary line. switches. t0 become'lockedw-it .their 111m` er shafts. Itis the function of the ev-ice...

(Fig. l1) to cause 'the rimary masteg'u switches to pick up their id e pl11r"\gex s v Its'l operation is4 as 4I ollovvszj .Associated witheach of the trunk` lines to which the secondary 'switches C2 `ha .v.fe ac-i. cesfs there isl a relay 75,. Only'threerelays'.` 75" anl '75 belongin totrunk lineS, which are accessible to t e switches con?. trolled .by the master switch D' .are fshown'; The relay 75 belongstov the rs't'trunk line 'of this "gr'oup,y the relay 7 5*.to'the trunk-A and the relay 75"'ptosome intern'le'diBtotxflll,`l ,siii` It" will be seen that when the 'switch C? opcrates to enga e the trunkconductorsf and 59, the relay '75 is ener ized over a circuit. from groun 'Grs through the' springs.' i 3 and 74 'and the relay. 75 tothe 75 ofeach rif-fthe other trunks' is energized f when its "trunkis .Seized-. The contact.'

of all the relays 7 5= to 75.are con- 95 are energizeda circuit isclosed fromground G* through the contacts of each of-the tre. .lays .75 in succession, and thence through the relay 77 to the battery lead 56. if The ref lay 77, uponl energizing, vs''aparetes the spri-ngs`78 and 79. and closes theeo'ntacjtsbe tween thesprings 80 and 8.1" and- 82 and 83. group' 'of trunk'lines. leading thereto. It

The' separation of the springs'78 and-79rdijsvconnects' the battery froxn'fthe s1enoi d 84 and 'from the spring 55 of the relay .8 5, so

erating. Thelclosing of the springs 82 and 8 3 closes e circuit 'through the rela 86 vwhich, upon energizing.. disconnects t e .battery `from all thcddlevv switches'C2 `which' are con-"11o trlled by the master switch D- and extends A y a'lonnection from ground G, back vthrough f the windngs49 of'said idle switchesto their j oorrespondlng eontects inthe bnks"of the in use; The closing of the springs-.811e d' tending?" from ground --G through Springs: ,81. 'a d- 80, andthencc tothe other; branch "passes th'roughf the' springsA 5 o'o battery lead 56;. In like manner, vthe frelay 1? l. forced VVinto contact by the operation of the' .limi

nel?.

0"to rest.

Wheel 91. The magnet 29, upon energizing, rotates the ratchet Wheel 91 and the wiper 27 one step, whereupon a circuit. is closed from ground G to the point 88. as just traced.v

6 thence through the wiper 27, contact point 93 and the relay 69 of the master switch D to the battery lead 56. The relay 69, upon energizing, closes the circuit of the relay 16. which in turn unlocks the plunger shaft and 10 permits it tooperate in the manner hereinbefore described. The relay 16 remains energized and the plunger shaft. of the master switch D continues to operate until the motor magnet 29 of the device L is energized i again to advance the wiper 27 asecondstel'i.

The magnet 29 is energized a second time by the cooperation oi the relays $20 and 92 in the following manner: The lrelay 96 is energized in series with the magnet 29 and,

20 upon energizing, operates to close the cir cuit of the relay 92. The relay 92, upon energizing,`separates the springs 8S), thereby yinterruliiting the circuit ot thc relay 90 and the magnet 2t). The magnet 29 deiinergizes 2 5 imn'lediatetv, but the relay 90 being a slo'w acting lrelay remains in its operated position for a short time. 1When the relay 90 finally deenergizes it interrupts the circuit ot' the relay 92, which also, being a slow acting relay, remains Vin its operated Vposition for an 135 cuit of the magnet 29 will be automatically interrupted to adrance the. wiper 27 step by step until said wiper strikes the bushing 04,

whereupon the operating circuit will be opened and the wiper 274 allowed to come its stop positions for a short interval of time owing to the slow. action of the relays 90 and 92. This interval is long enough to allow the master switch lDv to carry the plungers which it controls completely across their sets o bank contacts. 'When the plungers react the 4last trunk line, the arm 22 fpresses'the springs 23 and 24 into contact, thereby closing the circuit of the relay 95.

| This circuit extends from ground G3 through the s rings of the relay 69, springs 23 and 24, re ay .95 and the springs 72 to the battery llea-cl 56. The relay 95, upon energizing,

closes the circuit of the solenoid 12 which,

upon energizing, operates to restore the a0 t e plunger shaft reaches its starting position, the arm 21 unlocks the springs of the relay 95, thereby permitting the solenoid 12 to denergize.` It will thus be seen that the plunger shaft caused to complete its entire 'M movement atleast once, thereby causing all The wiper 27 remains in each of` the idle plungers which it controls to become locked in engagement therewith. so as -to be sure that none ot' thcm will bc lcl't stainling opposite a trunk line leading into the group ot secondary switchcs to which the switch (l2 belongs` all the trunk lines loading out from which arc assumed to hc busy. As shown in'thc dcvicc li. there is more than one contact cngagcd by thc wiper 2T in nay-h of its stop positions. Thus at each stcp said wiper causes a plurality of thc mastcr switches I) to operate to pick up thcir idle plungers. By thus having a number ot' contact points in cach position of the wiper :57. thc number of steps required to bc made b v said wiper is less than the total numbcz of master switches. and vot a large numbci` ofV switches arc not operated at oncc. thereby reducing the current consumption. 'hcn :in v one of the busy secondaryl switches Ct controlled by thc master switch l' is rclcascd, the rclay 75 ot' thc trunl; \\'hich was engaged by it becomcs denergizcd aud breaks thc circuit of the relay "7i The rcs lay 77, upon dcincrgizing. breaks the circuit ot' thc holding magnet' 30 ot the device li. which allows the pawl tlG'to he withdrawn from the ratchet wheel til to permit the wiper 27 to be restored toits normal position.

As hasbeen explained` the operation of the switches and C2, whichis initiated by the removal of the receiver' from the switch hook, extends the line coi'mection through to a first selector E. TheI calling subscriber now operates his calling dcvic'c in a wcll known manner for the successive digits ot' thc number of thc called line. The switch ll responds to the impulses tort-he trst digit` the selector lF-l'cspomls to th(` im pulses tor the second digit' and the connector ll operates in response to thc impulses i'or thc last; two digits to extend thc connection to thc called The operation of these switches is, in general. wcll understoodin the artand is 4fully described in British Patent No. 1421 of 151.10 previously referred to and it. is not thought necessary to describe the same in detail herein.

After a conversation is completed, the entire connection is autol'natically released by the hanging up of the receiver at the calling substation. This is brought about in the following manner: During the time the conversation is being carried on the release relays 97, 98 and 64 ot' the switches Il, F

audll are maintained energized by a circuit which is closed through the springs ot' the connector line relay 9S). When the calling subscriber hangs up his recciifer, the relay 09 denergizes and breaks the circuit of `th relays-97, 98 and 64. The relays 07,138 and 64, upon vdenergizig, operate to close the circuit ot the release magnets 100, 101 and. 102 of their respective switches. The re- 4riso ,leasemagneta .upon energizing, immediately 4 restore the switches lt9v normal position. lT he ing,' also destroysthe holding circuits of the-wiI'xdingsqGQ` and 68 of Vthe'. switches Y' C. and C, respectively, whereupon the plungers of said SWitchesa're permitted' to be restored '.to normal. position and alljthegapparfatus' yer-nployed inthe connection is leftin readi nessfor anotherl calllA 'Ift .will thus be' seen that;"I 'liavefdevised 4averyl eflicient system in whichit i'simpossible for aprimary line-1switchto seize anidle trunk vwhich extends intofa groupfofsecondary lineswit'ches when. all the trunks lead.-

'ingout of said secondary group are in use.

Thi'leII have illustrated'and .described my invention in connection Y ywith a. particular type. of telephone system and a articular type oflne switch, it Willl be lreadllypnderstood that my invention is notso limited,

I. .switches 'dividedg into groupsgja master in' use for causing any one of .sald master ondary trunk lines 'leading' out of .groups of secondary line switches, 1an'd. '.means 'operable When all the secondary trunk .as itis 'obvious that my invention is of broader scope, and I do not wish to-.be limited to the exact construction shown and described; y

What I claim asi my invention is:# .1; In. a -telephone system,..pr`imary line switch for .controlling each group of line switches, secondary .'ii1e. switches divided into groups,- tru'nk lines vleading-'from said primary to said. secondary-' line switches, 'sec said lines leading .outofa particular group are switches to vsweep over all of the trunk lines of a particular groupof primary switches `whilesorneof saldflast trunk lines are idle;

2'. '1'r .ia telephone System,'-a plurality-of groupsof primary line switches, a masten switch for controlling .each group, aplu-v rality. of i groups of` secondary line switches,

a secondary master switch for controlling line switches, tr'un lines leading'. from; said. primary tot.f said sec- -ing any one o f-said and .means oper-able -when* all the 'secondary es-:an'd distributed ainong ff am gemdur-line Y switches and mem rality. of.gro i1ps of secondary line switches,

group of secondary l'ine'switches are in ruse "of secondary line switches are inuse.

ity of groups of secondary .line s Agroup of--secondary line switch of saidprimary master` 'secondary trunk-limes of secondary line switches 'I. In a telephone system, a; plurality;fof. ;1 '15 'a plurality of boardsfo 'T .fpllllllty 0f.,switches, secondary. trunk lines "leading out oups'f ofAl secondary-f lineleading out of ii- 'partjicul'ar.grouper-e infuse forcausing any one of saidmnster switches particular group oflprimaryzswitohes While some of. vsaidv last lines are idle., 1 4, :L -telephone system a-plurality of groups'-yofprimaryline sw 1t`ches,`a master' switch'ifor controlling' each group, a plua secondary. master sw-itchfor controllin each group of secondary line switches, tran .lines leadngout` from veach group of pri- I'naryline's'witches and distributed among' a plurality of oups of secondary lme to s 'weeplover. all of. thet'r'unk -lines of 'a switches, 'secon' ary trunk lines leading out' I of each vgroup of secondary line switches, andmeans operable whenall of the second ary trunksvleading .out of awpa'rticular or causing. anyone of 'said primary master switches-to 'sweep over all of the trunk lines of a particular group of primary switches while some 'of said last trunk lines are idle.

5. 'In a telephone system, primary line switches divided into groups, a master Switch for controlling each group of line switches, secondary line switches divided f into groups, trunk lines leadingvfrom'said ondary -trunklines leadingolit of :said

groups of secondary' line switches, an

'means for successivelyoperating groups =o said-primary master 'switches when all th secondarytrunklines leading out of :,x. 1 rroup A 6.' I-n a telephone system, a plurality of" groups ofprimary' line switches, master switch for controlling each group vit'ohes, a. Ling each secondary m'aster switch for contro lines leading 'from said primaryLttondary line switches, secondary leading out of 'said and meansfor 'successi 'operating' groups tch'esvwhen allthe.

groups 4.of primar' line. switches, switch-for. 'control ing each griljup, ity -ofgroups lof .seocnfduryple manna-*laringe primary 'line:switchesif of said-.secondary line-1 Switches, for successively-. op-erating groups; of sai ding out of a group primar-Y .master 'switches .when "all the' 's'ee-"ifiZo i ofsecondary line -s'witehes;are in use..

8. ,Ina telephone lsystem`,a pluralityoff groups of 'primary' lme sw1tches,'a masterswitch for. controlling eacligroup, apluralj 1"'Jso u ity of groups of secondary line,V switches, a

l, lSecondary each i'oup ol secondary line switches. trunk master switch for controlling lilies eadiulf out Jfrom each. vrou i of iriv mary line. switches and distributed among a plurality ot' groups of secondary line switches. secondary truuh lines leading out ot' each group .of secondary line switches. and means t'or successively operating groups ot'` said p'riniary master switches when all the'secontlary trunk lines leading out of a tgronp ot' secondary line switches are in use.

l). ln a telephone. system. a. plurality ot groups ot' primary line switches. each of said line-switches including a plunger` a master switch t'or cach group-of primary line switches having ashaft with which said pllingers are normally iuicngageineut and adapted to'he disengaged therefrom upon the operation of said line switches', a group `et secondary line switches divided into groups. trunk lines leading from said pri: mary to said secondary line switches. secondary trunk lines leading out ot' said groups of secondary line. switches. and means operable when all the secondary trunks leadingpout of a group are in use l'oi causing any one ot' said mastery,switches to sweep over all of the trunk lines otl a particular group of priimary line switches to connect all the plungeis' with the corresponding sha It whilesoine -Iofsaidlast trunk lines are idle.

10.4 lu a telephone system. a plurality of `giauips of priu'iary line switches. cach of said line. switches including a plunger. a master switch `t'or each group ot' primary line switcheslhayi-ng a shatt with which said plungcrs are normally iu 'engagement and adapted to lie. disengaged theret'roni upon the operation ot said line switches. a group of secondary lline switches divided into groups,V trunk lines leading t'roin said priswitch for each group of primary lino switches having a shaft with which saidl plungers are normally in engagement and adapted to he disengaged therefrom upon the operation of said line switches. a group of secondary linoswitehes divided into groups, trunk lines leading from said primary to said secondary line switches. secondary trunk line;` leading out ol' said groups of secondary tine switches, means l'or operating said primary master switches to connect all the plungcrs of the line switches with the coriws|mnding shaft wlieu all the secondary trunlt's leading out ot' a group are in ilse, a rotary switch for successively -liringing groups of said master switches into operation. :unl means for delaying the operation ot said rotary switch.

1;. ln a telephone system. primary line switches divided into groups. a master switch for controlling each group. of line switches, secondary line switches lli-'vided into ,groups1 trunk lines leadingl t'roin said primary to said secondary line switches. secondary trunk lines leading/out of said groups of secondary line switches. means t'or successively operating groups 'otlsaid primary master switches when all the secondary trunk lines leadingr out of a group of secondary line` switches are in use. liauk contacts on said primary master switches corresponding t0 the trunhs leadingto said secondary switches. and meanst'or placing a guarding potential on said hank contacts ot' trunk lines extendiiigio a group of secondary line switches when allot' the. trunks leading out of said group-arc iii4 use. l

13. ln a telephone system. a plurality' of grouj'i's of primary liuc switches. a master switch for controlling eachV group. a pluralilil of groups of secondary liuc switches, a secondary master switch for controlling each group of secondary line switches. trunk lines leading from said primary to said sec! ondary line switches,secondarytrunk lines leading out of said econdary line switches, means t'or successiyeiy operating groups of said primary master' switches when all the. secondary trunk lines leading out of a grou of secondar line switches are in usaban' contactsl on said primary"master switches corresponding to the trunksleading tosaid secondary switches, and Un-leans for-placing a guarding potential oi aid liank .contacts of trunk lines extending to a group of secondary line switches when all of the trunks leading. out ofesaid group are in use.

'lol

asy

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14.- In a telephone;system.` a plurality of i groups of primaryline switches, a* master switch for controlling each group, a.plural ity of groups ot sectindary line switches, trunlclinesleading out from egh group of primary line switches and distributed among a .pluralityof groups of secondary line` .swt ches` secondary trunk lines leading out of'said secondary-line switches. means for successively,operating 'groups of said pri- .niary master switches when all the secondary trunk lines leading out of a. group of secondary line switches are in ilse. lianl con# ltacts on said primary master switches cor responding to the `trunks leading to said .secondary switches. and means for placing a guarding potential ou said hauk contacts of trunk lines extending to a group of sec;

o ncihry when all of the trunks f leading outofvsni'd'groupvare ir'rusc.A '152' In a .telephone system, a plurality. of

cach `groupof secondary line switches,trunk lines leading out from earchgroup of prilofmary line' switchesV end "distributed'among a plurslityof 'g roupsfof secondary line heSg--secqndary vtrunk Vlinesleading out uchl group .of secondary line"v switches for s cccss'ivelyoperating grou's vo ateriswltches when alli the line-switches are in use, ban 'Hlid mrmafy Switches. ngtbjthstmnks ledingto .said Isfvltches',"'midnieans for'pl'acing l ing pnbntial on said bank contacts of trunkl ladin'g'outofsd group ure in use. is i; 'groups ofiprimary line swltchedeach of said' A4inc switi'; es including@ plunger, @master switchcskhaving"'n` s hzift' Wit-h which said- 30 "plungers aire noxxnally in engagement and be dscngug'cd therefrom upon r-'dapdt.

thc. operation of sliddi-nel switches, a group fof 'secpndary-Vline I- switchesdivided' into ofseoondary line switches, means'for operating slid 'primary master switches to ti'u'xrk'lines lcading'outfo'fa grou' of secondary line switches divided "i'nto" qgronps, trunk .linesv leading from said pri- 16. In u, tels'phone systcm, a plurality of group are.l iniust''J rotary'A switch forsucces- 'siycly bringing groups of saidf master switches into operation, means for delaying 'the-operation o fl'said' rotary switch, bank corresponding to the trunks leading. to` said" .aryline switches w connect all plun rs o'f the line switches' thev igshafbwhen all the' s econdarytrunkslcading outof a' group are.

master switches corresponding to the trunks '46 lendingmo said secondary switches', and .Inca-ns' ,or placing aguarding potential` on f v sdgbrik contactsof trunk 11h68 extending to afgroup o f secondary' line switches; when llthetrunks leading outof-'said'gr'oup are' 5:0

in use.

17.1111 li-telephone systems plurality 'o'f groups of vprimary 'line' switchcs, each of `j'salid line switches *including -a plunger, `a

master switch for each group. of primary line 5o switches huving a shaft with whichA .said plngersjnre normally in cngagen1ent; and

fadsplted to be' disengaged therefrom upon the opcrationfof said line' switches, 'a group mary to said-sccondary'linc switches, seci ondary trunk Ilines. leading; out of said voups offseoondary line' switches, `Incensncsi-extendlng'to a group of seciixdry line'witche's'when 'all of the trunks I switchcsfwith the corresponding shaft whcn all the vsecondary trunks -l'esamding -out of va contactsy on said.I "primary, master 'switches secondary switches, Vand :means for placingn trunk linesextendinpflt"0 'aJ group of scconden all. of the trunks? 'lending out ofvsaid 'group'are in use.

"Sig'nsdb me at Los Angeles, LosAngeles so county, (la ifornia, this ten'th dny of'June,

cfs

7.5 guarding potential on said bankicont/cts of 

